The invention concerns rotary engines of the type shown in U.S. Pat. No. 2,988,065 and more particularly to rotary engines having a composite rotor construction, for example, as shown in U.S. Pat. No. 3,111,261 and No. 3,230,789. The rotors of such rotary engines are journaled on an eccentric portion of the engine shaft and said rotors have an internal gear connected thereto for meshing engagement with a fixed gear secured to the engine housing. Such rotors are generally made of a suitable aluminum alloy or other light-weight metal having good heat conducting properties. The gear and bearing sleeve for such a rotor are made of stronger material such as steel having lower heat conducting properties and are secured to the rotor hub. Accordingly, because the gear and bearing sleeve run cooler than the rotor since they are located at the rotor hub and because of the relatively lower thermal coefficient of the material of the gear and bearing sleeve, said gear and bearing sleeve will thermally expand and contract relative to the rotor. This differential expansion and contraction makes it difficult to adequately secure and rotatively locate the gear on the rotor.
As shown in aforementioned prior U.S. Pat. No. 3,111,261, the rotor is provided with a steel liner which has a tight shrink fit with the bore of the rotor. In addition, in said patent a combined rotor gear and bearing inner sleeve of steel material has a light interference fit within the steel liner such that this bearing sleeve floats at engine operating temperatures. Also, the inner bearing sleeve with its gear is splined to the rotor to maintain the relative rotative position of the gear on the rotor notwithstanding relative thermal expansion and contraction of the gear and rotor.
With this prior composite rotor construction of U.S. Pat. No. 3,111,261, since the rotor bearing sleeve to which the gear is attached floats radially in the rotor at engine operating temperatures, the splines rotatively locating the gear on the rotor can be subjected to severe stresses and possible fracture as a result of the combustion gas forces on the rotor when an engine working chamber fires. This is so because if the rotor bearing sleeve and gear are radially floating relative to the rotor, then when an engine working chamber fires, the rotor suddenly shifts under the combustion gas forces to take up the bearing clearance between the bearing sleeve and rotor and as a result the rotor suddenly strikes the bearing sleeve thereby possibly severely stressing the splines locating the rotor gear, depending on the circumferential position and clearance of these splines.
With the composite rotor construction of prior U.S. Pat. No. 3,230,789, the rotor has an inner sleeve which has a radial spline connection to the rotor hub to accommodate relative thermal expansion and contraction of the rotor gear which is rigidly attached to this sleeve. Accordingly, in this prior patent the radial spline connection between said inner sleeve and rotor hub transmits the combustion gas forces to the eccentric of the engine shaft on which the rotor is journaled and, therefore, these splines are also subject to severe stresses particularly because of the magnitude of the combustion gas forces. Accordingly, with the construction of U.S. Pat. No. 3,230,789, in order to withstand these forces, the splines have to extend entirely across the rotor, and in addition, the splines have to be accurately mated together, for example, by casting the rotor about the sleeve splines or by extremely accurate machining thereby resulting in a costly construction.